Because crapping on Mongo is “in” right now. Years ago it used to be “in” to crap on it for its deaign choices, especially its tendency to lose data (seems to be what the parent comment is referencing; see [1] for a summary of some issues from 2013).
More recently it’s “in” for their business decisions, with the relicensing and the rise of API-compatible alternatives pushing some users away.
But yeah, really no reason to mock them in this discussion, apart from going for internet cool points from an audience that may also be critical of Mongo.